TROFF(1) TROFF(1)
NAME
troff - format documents
SYNOPSIStroff [ -abivzCER ] [ -wname ] [ -Wname ] [ -dcs ]
[ -ffam ] [ -mname ] [ -nnum ] [ -olist ] [ -rcn ]
[ -Tname ] [ -Fdir ] [ -Mdir ] [ files... ]
DESCRIPTION
This manual page describes the GNU version of troff, which
is part of the groff document formatting system. It is
highly compatible with Unix troff. Usually it should be
invoked using the groff command, which will also run pre-
processors and postprocessors in the appropriate order and
with the appropriate options.
OPTIONS-a Generate an ASCII approximation of the typeset
output.
-b Print a backtrace with each warning or error
message. This backtrace should help track down
the cause of the error. The line numbers given
in the backtrace may not always correct: troff's
idea of line numbers gets confused by as or am
requests.
-i Read the standard input after all the named
input files have been processed.
-v Print the version number.
-wname Enable warning name. Available warnings are
described in the Warnings subsection below.
Multiple -w options are allowed.
-Wname Inhibit warning name. Multiple -W options are
allowed.
-E Inhibit all error messages.
-z Suppress formatted output.
-C Enable compatibility mode.
-dcs-dname=s Define c or name to be a string s; c must be a
one letter name.
-ffam Use fam as the default font family.
-mname Read in the file tmac.name. Normally this will
be searched for in /usr/lib/groff/tmac.
-R Don't load troffrc.
-nnum Number the first page num.
-olist Output only pages in list, which is a comma-sep-
arated list of page ranges; n means print page
n, m-n means print every page between m and n,
-n means print every page up to n, n- means
print every page from n. Troff will exit after
printing the last page in the list.
-rcn-rname=n Set number register c or name to n; c must be a
one character name; n can be any troff numeric
expression.
-Tname Prepare output for device name, rather than the
default ps.
-Fdir Search dir for subdirectories devname (name is
the name of the device) for the DESC file and
font files before the normal
/usr/lib/groff/font.
-Mdir Search directory dir for macro files before the
normal /usr/lib/groff/tmac.
USAGE
Only the features not in Unix troff are described here.
Longnames
The names of number registers, fonts,
strings/macros/diversions, special characters can be of
any length. In escape sequences, where you can use (xx for
a two character name, you can use [xxx] for a name of
arbitrary length:
\[xxx] Print the special character called xxx.
\f[xxx]
Set font xxx.
\*[xxx]
Interpolate string xxx.
\n[xxx]
Interpolate number register xxx.
Fractionalpointsizes
A scaledpoint is equal to 1/sizescale points, where
sizescale is specified in the DESC file (1 by default.)
There is a new scale indicator z which has the effect of
multiplying by sizescale. Requests and escape sequences
in troff interpret arguments that represent a pointsize as
being in units of scaled points, but they evaluate each
such argument using a default scale indicator of z. Argu-
ments treated in this way are the argument to the ps
request, the third argument to the cs request, the second
and fourth arguments to the tkf request, the argument to
the \H escape sequence, and those variants of the \s
escape sequence that take a numeric expression as their
argument.
For example, suppose sizescale is 1000; then a scaled
point will be equivalent to a millipoint; the request .ps10.25 is equivalent to .ps10.25z and so sets the point-
size to 10250 scaled points, which is equal to 10.25
points.
The number register \n(.s returns the pointsize in points
as decimal fraction. There is also a new number register
\n[.ps] that returns the pointsize in scaled points.
It would make no sense to use the z scale indicator in a
numeric expression whose default scale indicator was nei-
ther u nor z, and so troff disallows this. Similarly it
would make no sense to use a scaling indicator other than
z or u in a numeric expression whose default scale indica-
tor was z, and so troff disallows this as well.
There is also new scale indicator s which multiplies by
the number of units in a scaled point. So, for example,
\n[.ps]s is equal to 1m. Be sure not to confuse the s and
z scale indicators.
Numericexpressions
Spaces are permitted in a number expression within paren-
theses.
M indicates a scale of 100ths of an em.
e1>?e2 The maximum of e1 and e2.
e1<?e2 The minimum of e1 and e2.
(c;e) Evaluate e using c as the default scaling indica-
tor. If c is missing, ignore scaling indicators in
the evaluation of e.
Newescapesequences\A'anything'
This expands to 1 or 0 according as anything is or
is not acceptable as the name of a string, macro,
diversion, number register, environment or font.
It will return 0 if anything is empty. This is
useful if you want to lookup user input in some
sort of associative table.
\C'xxx'
Typeset character named xxx. Normally it is more
convenient to use \[xxx]. But \C has the advantage
that it is compatible with recent versions of UNIX
and is available in compatibility mode.
\E This is equivalent to an escape character, but it's
not interpreted in copy-mode. For example, strings
to start and end superscripting could be defined
like this:
.ds { \v'-.3m'\s'\En[.s]*6u/10u'
.ds } \s0\v'.3m'
The use of \E ensures that these definitions will
work even if \*{ gets interpreted in copy-mode (for
example, by being used in a macro argument.)
\N'n' Typeset the character with code n in the current
font. n can be any integer. Most devices only
have characters with codes between 0 and 255. If
the current font does not contain a character with
that code, special fonts will not be searched. The
\N escape sequence can be conveniently used on con-
junction with the char request:
.char\[phone]\f(ZD\N'37'
The code of each character is given in the fourth
column in the font description file after the
charset command. It is possible to include unnamed
characters in the font description file by using a
name of ---; the \N escape sequence is the only way
to use these.
\R'name+-n'
This has the same effect as
.nrname+-n\s(nn\s+-(nn
Set the point size to nn points; nn must be exactly
two digits.
\s[+-n]\s+-[n]\s'+-n'\s+-'n'
Set the point size to n scaled points; n is a
numeric expression with a default scale indicator
of z.
\Vx\V(xx\V[xxx]
Interpolate the contents of the environment vari-
able xxx, as returned by getenv(3). \V is inter-
preted in copy-mode.
\Yx\Y(xx\Y[xxx]
This is approximately equivalent to \X'\*[xxx]'.
However the contents of the string or macro xxx are
not interpreted; also it is permitted for xxx to
have been defined as a macro and thus contain new-
lines (it is not permitted for the argument to \X
to contain newlines). The inclusion of newlines
requires an extension to the Unix troff output for-
mat, and will confuse drivers that do not know
about this extension.
\Z'anything'
Print anything and then restore the horizontal and
vertical position; anything may not contain tabs or
leaders.
\$0 The name by which the current macro was invoked.
The als request can make a macro have more than one
name.
\$* In a macro, the concatenation of all the arguments
separated by spaces.
\$@ In a macro, the concatenation of all the arguments
with each surrounded by double quotes, and sepa-
rated by spaces.
\$(nn\$[nnn]
In a macro, this gives the nn-th or nnn-th argu-
ment. Macros can have a unlimited number of argu-
ments.
\?anything\?
When used in a diversion, this will transparently
embed anything in the diversion. anything is read
in copy mode. When the diversion is reread, any-thing will be interpreted. anything may not con-
tain newlines; use \! if you want to embed new-
lines in a diversion. The escape sequence \? is
also recognised in copy mode and turned into a sin-
gle internal code; it is this code that terminates
anything. Thus
.nrx1.nf.did\?\\?\\\\?\\\\\\\\nx\\\\?\\?\?.di.nrx2.die.d.di.nrx3.dif.e.di.nrx4.f
will print 4.
\/ This increases the width of the preceding character
so that the spacing between that character and the
following character will be correct if the follow-
ing character is a roman character. For example,
if an italic f is immediately followed by a roman
right parenthesis, then in many fonts the top right
portion of the f will overlap the top left of the
right parenthesis producing f), which is ugly.
Inserting \/ produces f) and avoids this problem.
It is a good idea to use this escape sequence when-
ever an italic character is immediately followed by
a roman character without any intervening space.
\, This modifies the spacing of the following charac-
ter so that the spacing between that character and
the preceding character will correct if the preced-
ing character is a roman character. For example,
inserting \, between the parenthesis and the f
changes (f to (f. It is a good idea to use this
escape sequence whenever a roman character is imme-
diately followed by an italic character without any
intervening space.
\) Like \& except that it behaves like a character
declared with the cflags request to be transparent
for the purposes of end of sentence recognition.
\~ This produces an unbreakable space that stretches
like a normal inter-word space when a line is
adjusted.
\# Everything up to and including the next newline is
ignored. This is interpreted in copy mode. This
is like \" except that \" does not ignore the ter-
minating newline.
Newrequests.alnxxyy
Create an alias xx for number register object named
yy. The new name and the old name will be exactly
equivalent. If yy is undefined, a warning of type
reg will be generated, and the request will be
ignored.
.alsxxyy
Create an alias xx for request, string, macro, or
diversion object named yy. The new name and the
old name will be exactly equivalent (it is similar
to a hard rather than a soft link). If yy is unde-
fined, a warning of type mac will be generated, and
the request will be ignored. The de, am, di, da,
ds, and as requests only create a new object if the
name of the macro, diversion or string diversion is
currently undefined or if it is defined to be a
request; normally they modify the value of an
existing object.
.asciifyxx
This request only exists in order to make it possi-
ble to make certain gross hacks work with GNU
troff. It `unformats' the diversion xx in such a
way that ASCII characters that were formatted and
diverted into xx will be treated like ordinary
input characters when xx is reread. For example,
this
.tr@..dix@nr\n\1.br.di.tr@@.asciifyx.x
will set register n to 1.
.backtrace
Print a backtrace of the input stack on stderr.
.blmxx
Set the blank line macro to xx. If there is a
blank line macro, it will be invoked when a blank
line is encountered instead of the usual troff
behaviour.
.break Break out of a while loop. See also the while and
continue requests. Be sure not to confuse this
with the br request.
.cflagsnc1c2...
Characters c1, c2,... have properties determined
by n, which is ORed from the following:
1 the character ends sentences (initially
characters .?! have this property);
2 lines can be broken before the character
(initially no characters have this prop-
erty); a line will not be broken at a char-
acter with this property unless the charac-
ters on each side both have non-zero hyphen-
ation codes.
4 lines can be broken after the character
(initially characters -\(hy\(em have this
property); a line will not be broken at a
character with this property unless the
characters on each side both have non-zero
hyphenation codes.
8 the character overlaps horizontally (ini-
tially characters \(ul\(rn\(ru have this
property);
16 the character overlaps vertically (initially
character \(br has this property);
32 an end of sentence character followed by any
number of characters with this property will
be treated as the end of a sentence if fol-
lowed by a newline or two spaces; in other
words the character is transparent for the
purposes of end of sentence recognition;
this is the same as having a zero space fac-
tor in TeX (initially characters
"')]*\(dg\(rq have this property).
.charcstring
Define character c to be string. Every time char-
acter c needs to be printed, string will be pro-
cessed in a temporary environment and the result
will be wrapped up into a single object. Compati-
bility mode will be turned off and the escape char-
acter will be set to \ while string is being pro-
cessed. Any emboldening, constant spacing or track
kerning will be applied to this object rather than
to individual characters in string. A character
defined by this request can be used just like a
normal character provided by the output device. In
particular other characters can be translated to it
with the tr request; it can be made the leader
character by the lc request; repeated patterns can
be drawn with the character using the \l and \L
escape sequences; words containing the character
can be hyphenated correctly, if the hcode request
is used to give the character a hyphenation code.
There is a special anti-recursion feature: use of
character within the character's definition will be
handled like normal characters not defined with
char. A character definition can be removed with
the rchar request.
.chopxx
Chop the last character off macro, string, or
diversion xx. This is useful for removing the new-
line from the end of diversions that are to be
interpolated as strings.
.closestream
Close the stream named stream; stream will no
longer be an acceptable argument to the write
request. See the open request.
.continue
Finish the current iteration of a while loop. See
also the while and break requests.
.cpn If n is non-zero or missing, enable compatibility
mode, otherwise disable it. In compatibility mode,
long names are not recognised, and the incompati-
bilities caused by long names do not arise.
.doxxx
Interpret .xxx with compatibility mode disabled.
For example,
.dofamT
would have the same effect as
.famT
except that it would work even if compatibility
mode had been enabled. Note that the previous com-
patibility mode is restored before any files
sourced by xxx are interpreted.
.famxx
Set the current font family to xx. The current
font family is part of the current environment.
See the description of the sty request for more
information on font families.
.fspecialfs1s2...
When the current font is f, fonts s1, s2,... will
be special, that is, they will searched for charac-
ters not in the current font. Any fonts specified
in the special request will be searched after fonts
specified in the fspecial request.
.ftrfg
Translate font f to g. Whenever a font named f is
referred to in \f escape sequence, or in the ft,
ul, bd, cs, tkf, special, fspecial, fp, or sty
requests, font g will be used. If g is missing, or
equal to f then font f will not be translated.
.hcodec1code1c2code2...
Set the hyphenation code of character c1 to code1
and that of c2 to code2. A hyphenation code must
be a single input character (not a special charac-
ter) other than a digit or a space. Initially each
lower-case letter has a hyphenation code, which is
itself, and each upper-case letter has a hyphen-
ation code which is the lower case version of
itself. See also the hpf request.
.hlalang
Set the current hyphenation language to lang.
Hyphenation exceptions specified with the hw
request and hyphenation patterns specified with the
hpf request are both associated with the current
hyphenation language. The hla request is usually
invoked by the troffrc file.
.hlmn Set the maximum number of consecutive hyphenated
lines to n. If n is negative, there is no maximum.
The default value is -1. This value is associated
with the current environment. Only lines output
from an environment count towards the maximum asso-
ciated with that environment. Hyphens resulting
from \% are counted; explicit hyphens are not.
.hpffile
Read hyphenation patterns from file; this will be
searched for in the same way that tmac.name is
searched for when the -mname option is specified.
It should have the same format as the argument to
the \patterns primitive in TeX; the letters appear-
ing in this file are interpreted as hyphenation
codes. A % character in the patterns file intro-
duces a comment that continues to the end of the
line. The set of hyphenation patterns is associ-
ated with the current language set by the hla
request. The hpf request is usually invoked by the
troffrc file.
.hymn Set the hyphenationmargin to n: when the current
adjustment mode is not b, the line will not be
hyphenated if the line is no more than n short.
The default hyphenation margin is 0. The default
scaling indicator for this request is m. The
hyphenation margin is associated with the current
environment. The current hyphenation margin is
available in the \n[.hym] register.
.hysn Set the hyphenationspace to n: when the current
adjustment mode is b don't hyphenate the line if
the line can be justified by adding no more than n
extra space to each word space. The default
hyphenation space is 0. The default scaling indi-
cator for this request is m. The hyphenation space
is associated with the current environment. The
current hyphenation space is available in the
\n[.hys] register.
.kernn
If n is non-zero or missing, enable pairwise kern-
ing, otherwise disable it.
.msofile
The same as the so request except that file is
searched for in the same way that tmac.name is
searched for when the -mname option is specified.
.nroff Make the n built-in condition true and the t built-
in condition false. This can be reversed using the
troff request.
.openstreamfilename
Open filename for writing and associate the stream
named stream with it. See also the close and write
requests.
.openastreamfilename
Like open, but if filename exists, append to it
instead of truncating it.
.pnr Print the names and contents of all currently
defined number registers on stderr.
.psocommand
This is behaves like the so request except that
input comes from the standard output of command.
.ptr Print the names and positions of all traps (not
including input line traps and diversion traps) on
stderr. Empty slots in the page trap list are
printed as well, because they can affect the prior-
ity of subsequently planted traps.
.rcharc1c2...
Remove the definitions of characters c1, c2,...
This undoes the effect of a char request.
.rj.rjn Right justify the next n input lines. Without an
argument right justify the next input line. The
number of lines to be right justified is available
in the \n[.rj] register. This implicitly does
.ce0. The ce request implicitly does .rj0.
.rnnxxyy
Rename number register xx to yy.
.shcc Set the soft hyphen character to c. If c is omit-
ted, the soft hyphen character will be set to the
default \(hy. The soft hyphen character is the
character which will be inserted when a word is
hyphenated at a line break. If the soft hyphen
character does not exist in the font of the charac-
ter immediately preceding a potential break point,
then the line will not be broken at that point.
Neither definitions (specified with the char
request) nor translations (specified with the tr
request) are considered when finding the soft
hyphen character.
.shiftn
In a macro, shift the arguments by n positions:
argument i becomes argument i-n; arguments 1 to n
will no longer be available. If n is missing,
arguments will be shifted by 1. Shifting by nega-
tive amounts is currently undefined.
.specials1s2...
Fonts s1, s2, are special and will be searched for
characters not in the current font.
.stynf
Associate style f with font position n. A font
position can be associated either with a font or
with a style. The current font is the index of a
font position and so is also either a font or a
style. When it is a style, the font that is actu-
ally used is the font the name of which is the con-
catenation of the name of the current family and
the name of the current style. For example, if the
current font is 1 and font position 1 is associated
with style R and the current font family is T, then
font TR will be used. If the current font is not a
style, then the current family is ignored. When
the requests cs, bd, tkf, uf, or fspecial are
applied to a style, then they will instead be
applied to the member of the current family corre-
sponding to that style. The default family can be
set with the -f option. The styles command in the
DESC file controls which font positions (if any)
are initially associated with styles rather than
fonts.
.tkffs1n1s2n2
Enable track kerning for font f. When the current
font is f the width of every character will be
increased by an amount between n1 and n2; when the
current point size is less than or equal to s1 the
width will be increased by n1; when it is greater
than or equal to s2 the width will be increased by
n2; when the point size is greater than or equal to
s1 and less than or equal to s2 the increase in
width is a linear function of the point size.
.trffilename
Transparently output the contents of file filename.
Each line is output as it would be were it preceded
by \!; however, the lines are not subject to copy-
mode interpretation. If the file does not end with
a newline, then a newline will be added. For exam-
ple, you can define a macro x containing the con-
tents of file f, using
.dix.trff.di
Unlike with the cf request, the file cannot contain
characters such as NUL that are not legal troff
input characters.
.trntabcd
This is the same as the tr request except that the
translations do not apply to text that is transpar-
ently throughput into a diversion with \!. For
example,
.trab.dix\!.tma.di.x
will print b; if trnt is used instead of tr it will
print a.
.troff Make the n built-in condition false, and the t
built-in condition true. This undoes the effect of
the nroff request.
.vptn Enable vertical position traps if n is non-zero,
disable them otherwise. Vertical position traps
are traps set by the wh or dt requests. Traps set
by the it request are not vertical position traps.
The parameter that controls whether vertical posi-
tion traps are enabled is global. Initially verti-
cal position traps are enabled.
.warnn
Control warnings. n is the sum of the numbers
associated with each warning that is to be enabled;
all other warnings will be disabled. The number
associated with each warning is listed in the
`Warnings' section. For example, .warn0 will dis-
able all warnings, and .warn1 will disable all
warnings except that about missing characters. If
n is not given, all warnings will be enabled.
.whilecanything
While condition c is true, accept anything as
input; c can be any condition acceptable to an if
request; anything can comprise multiple lines if
the first line starts with \{ and the last line
ends with \}. See also the break and continue
requests.
.writestreamanything
Write anything to the stream named stream. stream
must previously have been the subject of an open
request. anything is read in copy mode; a leading
" will be stripped.
Extendedrequests.cffilename
When used in a diversion, this will embed in the
diversion an object which, when reread, will cause
the contents of filename to be transparently copied
through to the output. In Unix troff, the contents
of filename is immediately copied through to the
output regardless of whether there is a current
diversion; this behaviour is so anomalous that it
must be considered a bug.
.evxx If xx is not a number, this will switch to a named
environment called xx. The environment should be
popped with a matching ev request without any argu-
ments, just as for numbered environments. There is
no limit on the number of named environments; they
will be created the first time that they are refer-
enced.
.fpnf1f2
The fp request has an optional third argument.
This argument gives the external name of the font,
which is used for finding the font description
file. The second argument gives the internal name
of the font which is used to refer to the font in
troff after it has been mounted. If there is no
third argument then the internal name will be used
as the external name. This feature allows you to
use fonts with long names in compatibility mode.
.ssmn
When two arguments are given to the ss request, the
second argument gives the sentencespacesize. If
the second argument is not given, the sentence
space size will be the same as the word space size.
Like the word space size, the sentence space is in
units of one twelfth of the spacewidth parameter
for the current font. Initially both the word
space size and the sentence space size are 12. The
sentence space size is used in two circumstances:
if the end of a sentence occurs at the end of a
line in fill mode, then both an inter-word space
and a sentence space will be added; if two spaces
follow the end of a sentence in the middle of a
line, then the second space will be a sentence
space. Note that the behaviour of Unix troff will
be exactly that exhibited by GNU troff if a second
argument is never given to the ss request. In GNU
troff, as in Unix troff, you should always follow a
sentence with either a newline or two spaces.
.tan1n2...nnTr1r2...rn
Set tabs at positions n1, n2,..., nn and then set
tabs at nn+r1, nn+r2,...., nn+rn and then at
nn+rn+r1, nn+rn+r2,..., nn+rn+rn, and so on. For
example,
.taT.5i
will set tabs every half an inch.
Newnumberregisters
The following read-only registers are available:
\n[.C] 1 if compatibility mode is in effect, 0 otherwise.
\n[.cdp]
The depth of the last character added to the cur-
rent environment. It is positive if the character
extends below the baseline.
\n[.ce]
The number of lines remaining to be centered, as
set by the ce request.
\n[.cht]
The height of the last character added to the cur-
rent environment. It is positive if the character
extends above the baseline.
\n[.csk]
The skew of the last character added to the current
environment. The skew of a character is how far to
the right of the center of a character the center
of an accent over that character should be placed.
\n[.ev]
The name or number of the current environment.
This is a string-valued register.
\n[.fam]
The current font family. This is a string-valued
register.
\n[.fp]
The number of the next free font position.
\n[.g] Always 1. Macros should use this to determine
whether they are running under GNU troff.
\n[.hla]
The current hyphenation language as set by the hla
request.
\n[.hlc]
The number of immediately preceding consecutive
hyphenated lines.
\n[.hlm]
The maximum allowed number of consecutive hyphen-
ated lines, as set by the hlm request.
\n[.hy]
The current hyphenation flags (as set by the hy
request.)
\n[.hym]
The current hyphenation margin (as set by the hym
request.)
\n[.hys]
The current hyphenation space (as set by the hys
request.)
\n[.in]
The indent that applies to the current output line.
\n[.kern]1 if pairwise kerning is enabled, 0 otherwise.
\n[.lg]
The current ligature mode (as set by the lg
request.)
\n[.ll]
The line length that applies to the current output
line.
\n[.lt]
The title length as set by the lt request.
\n[.ne]
The amount of space that was needed in the last ne
request that caused a trap to be sprung. Useful in
conjunction with the \n[.trunc] register.
\n[.pn]
The number of the next page: either the value set
by a pn request, or the number of the current page
plus 1.
\n[.ps]
The current pointsize in scaled points.
\n[.psr]
The last-requested pointsize in scaled points.
\n[.rj]
The number of lines to be right-justified as set by
the rj request.
\n[.sr]
The last requested pointsize in points as a decimal
fraction. This is a string-valued register.
\n[.tabs]
A string representation of the current tab settings
suitable for use as an argument to the ta request.
\n[.trunc]
The amount of vertical space truncated by the most
recently sprung vertical position trap, or, if the
trap was sprung by a ne request, minus the amount
of vertical motion produced by the ne request. In
other words, at the point a trap is sprung, it rep-
resents the difference of what the vertical posi-
tion would have been but for the trap, and what the
vertical position actually is. Useful in conjunc-
tion with the \n[.ne] register.
\n[.ss]\n[.sss]
These give the values of the parameters set by the
first and second arguments of the ss request.
\n[.vpt]
1 if vertical position traps are enabled, 0 other-
wise.
\n[.warn]
The sum of the numbers associated with each of the
currently enabled warnings. The number associated
with each warning is listed in the `Warnings' sub-
section.
\n(.x The major version number. For example, if the ver-
sion number is 1.03 then \n(.x will contain 1.
\n(.y The minor version number. For example, if the ver-
sion number is 1.03 then \n(.y will contain 03.
The following registers are set by the \w escape sequence:
\n[rst]\n[rsb]
Like the st and sb registers, but takes account of
the heights and depths of characters.
\n[ssc]
The amount of horizontal space (possibly negative)
that should be added to the last character before a
subscript.
\n[skw]
How far to right of the center of the last charac-
ter in the \w argument, the center of an accent
from a roman font should be placed over that char-
acter.
The following read/write number registers are available:
\n[systat]
The return value of the system() function executed
by the last sy request.
\n[slimit]
If greater than 0, the maximum number of objects on
the input stack. If less than or equal to 0, there
is no limit on the number of objects on the input
stack. With no limit, recursion can continue until
virtual memory is exhausted.
Miscellaneous
Fonts not listed in the DESC file are automatically
mounted on the next available font position when they are
referenced. If a font is to be mounted explicitly with
the fp request on an unused font position, it should be
mounted on the first unused font position, which can be
found in the \n[.fp] register; although troff does not
enforce this strictly, it will not allow a font to be
mounted at a position whose number is much greater than
that of any currently used position.
Interpolating a string does not hide existing macro argu-
ments. Thus in a macro, a more efficient way of doing
.xx\\$@
is
\\*[xx]\\
If the font description file contains pairwise kerning
information, characters from that font will be kerned.
Kerning between two characters can be inhibited by placing
a \& between them.
In a string comparison in a condition, characters that
appear at different input levels to the first delimiter
character will not be recognised as the second or third
delimiters. This applies also to the tl request. In a \w
escape sequence, a character that appears at a different
input level to the starting delimiter character will not
be recognised as the closing delimiter character. When
decoding a macro argument that is delimited by double
quotes, a character that appears at a different input
level to the starting delimiter character will not be
recognised as the closing delimiter character. The imple-
mentation of \$@ ensures that the double quotes surround-
ing an argument will appear the same input level, which
will be different to the input level of the argument
itself. In a long escape name ] will not be recognized as
a closing delimiter except when it occurs at the same
input level as the opening ]. In compatibility mode, no
attention is paid to the input-level.
There are some new types of condition:
.ifrxxx
True if there is a number register named xxx.
.ifdxxx
True if there is a string, macro, diversion, or
request named xxx.
.ifcch
True if there is a character ch available; ch is
either an ASCII character or a special character
\(xx or \[xxx]; the condition will also be true if
ch has been defined by the char request.
Warnings
The warnings that can be given by troff are divided into
the following categories. The name associated with each
warning is used by the -w and -W options; the number is
used by the warn request, and by the .warn register.
char 1 Non-existent characters. This is
enabled by default.
number 2 Invalid numeric expressions. This is
enabled by default.
break 4 In fill mode, lines which could not be
broken so that their length was less
than the line length. This is enabled
by default.
delim 8 Missing or mismatched closing delim-
iters.
el 16 Use of the el request with no matching
ie request.
scale 32 Meaningless scaling indicators.
range 64 Out of range arguments.
syntax 128 Dubious syntax in numeric expressions.
di 256 Use of di or da without an argument
when there is no current diversion.
mac 512 Use of undefined strings, macros and
diversions. When an undefined string,
macro or diversion is used, that string
is automatically defined as empty. So,
in most cases, at most one warning will
be given for each name.
reg 1024 Use of undefined number registers.
When an undefined number register is
used, that register is automatically
defined to have a value of 0. a defi-
nition is automatically made with a
value of 0. So, in most cases, at most
one warning will be given for use of a
particular name.
tab 2048 Inappropriate use of a tab character.
Either use of a tab character where a
number was expected, or use of tab
character in an unquoted macro argu-
ment.
right-brace 4096 Use of \} where a number was expected.
missing 8192 Requests that are missing non-optional
arguments.
input 16384 Illegal input characters.
escape 32768 Unrecognized escape sequences. When an
unrecognized escape sequence is encoun-
tered, the escape character is ignored.
space 65536 Missing space between a request or
macro and its argument. This warning
will be given when an undefined name
longer than two characters is encoun-
tered, and the first two characters of
the name make a defined name. The
request or macro will not be invoked.
When this warning is given, no macro is
automatically defined. This is enabled
by default. This warning will never
occur in compatibility mode.
font 131072 Non-existent fonts. This is enabled by
default.
ig 262144 Illegal escapes in text ignored with
the ig request. These are conditions
that are errors when they do not occur
in ignored text.
There are also names that can be used to refer to groups
of warnings:
all All warnings except di, mac and reg. It is
intended that this covers all warnings that are
useful with traditional macro packages.
w All warnings.
Incompatibilities
Long names cause some incompatibilities. Unix troff will
interpret
.dsabcd
as defining a string ab with contents cd. Normally, GNU
troff will interpret this as a call of a macro named
dsabcd. Also Unix troff will interpret \*[ or \n[ as ref-
erences to a string or number register called [. In GNU
troff, however, this will normally be interpreted as the
start of a long name. In compatibilitymode GNU troff
will interpret these things in the traditional way. In
compatibility mode, however, long names are not recog-
nised. Compatibility mode can be turned on with the -C
command line option, and turned on or off with the cp
request. The number register \n(.C is 1 if compatibility
mode is on, 0 otherwise.
GNU troff does not allow the use of the escape sequences
\\|\^\&\}\{\(space)\'\`\-\_\!\%\c in names of strings,
macros, diversions, number registers, fonts or environ-
ments; Unix troff does. The \A escape sequence may be
helpful in avoiding use of these escape sequences in
names.
Fractional pointsizes cause one noteworthy incompatibil-
ity. In Unix troff the ps request ignores scale indica-
tors and so
.ps10u
will set the pointsize to 10 points, whereas in GNU troff
it will set the pointsize to 10 scaled points.
In GNU troff there is a fundamental difference between
unformatted, input characters, and formatted, output char-
acters. Everything that affects how an output character
will be output is stored with the character; once an out-
put character has been constructed it is unaffected by any
subsequent requests that are executed, including bd, cs,
tkf, tr, or fp requests. Normally output characters are
constructed from input characters at the moment immedi-
ately before the character is added to the current output
line. Macros, diversions and strings are all, in fact,
the same type of object; they contain lists of input char-
acters and output characters in any combination. An out-
put character does not behave like an input character for
the purposes of macro processing; it does not inherit any
of the special properties that the input character from
which it was constructed might have had. For example,
.dix\\\\.br.di.x
will print \\ in GNU troff; each pair of input \s is
turned into one output \ and the resulting output \s are
not interpreted as escape characters when they are reread.
Unix troff would interpret them as escape characters when
they were reread and would end up printing one \. The
correct way to obtain a printable \ is to use the \e
escape sequence: this will always print a single instance
of the current escape character, regardless of whether or
not it is used in a diversion; it will also work in both
GNU troff and Unix troff. If you wish for some reason to
store in a diversion an escape sequence that will be
interpreted when the diversion is reread, you can either
use the traditional \! transparent output facility, or,
if this is unsuitable, the new \? escape sequence.
ENVIRONMENTGROFF_TMAC_PATH
A colon separated list of directories in which to
search for macro files.
GROFF_TYPESETTER
Default device.
GROFF_FONT_PATH
A colon separated list of directories in which to
search for the devname directory. troff will
search in directories given in the -F option before
these, and in standard directories
(.:/usr/lib/groff/font:/usr/lib/font) after these.
FILES/usr/lib/groff/tmac/troffrc
Initialization file
/usr/lib/groff/tmac/tmac.name
Macro files
/usr/lib/groff/font/devname/DESC
Device description file for device name.
/usr/lib/groff/font/devname/F
Font file for font F of device name.
SEEALSOgroff(1) tbl(1), pic(1), eqn(1), grops(1), grodvi(1),
grotty(1), groff_font(5), groff_out(5), groff_char(7)
Groff Version 1.11 26 June 1995 1